Experiments designed to investigate the nature of oxidation-reduction reactions of copper with respiratory cytochromes and related model compounds are described. A major objective is to provide experimental evidence useful in assessing the validity of various hypotheses advanced to account for apparent long-range electron transfer in these reactions. Particular attention is given to evaluating the potential role of isoprenyl functional groups in mediating electron transfer. Impetus for the study derives from the recent structural characterization of heme a and our own work on the spectra and redox kinetics of copper(I)-transition metal oxidant binuclear ions containing copper pi-coordinated to the olefin groups on the bridging ligand. Based upon characterization of the physical properties of Cu(I)-olefin complexes, including heme a-copper ions, evidence for similar structural organization will be sought in cytochrome oxidase. New spectroscopic and rapid-kinetic methods potentially useful in probing the nature of cooperative interactions between metal centers in multiredox equivalent biological particles are also described and will be applied to the study of cytochrome oxidase. DTX* 1GM-21359-3*